INVERTEBRATE PALAEONTOLOGY. 429 



(tig. 3, r). particularly in the form of its third lateral lobe, and the presence 

 of a small fourth lateral. 



Compared with Dr. Owen's typical form of & nodosus, it will be seen 

 to differ even more strongly than the last, in form and several other respects. 



Still, I have been unable fully to convince myself that, like the last, it is 

 not a small, shorter variety of the same species. 



Some specimens of this variety, such as that represented by our figures 

 2, a, b, are more compressed than that for which the variety-name quadran- 

 gularis was proposed, but agree nearly in other respects. These are even 

 more nearly like d'Orbigny's figures of & cons/rictus than the last, but they 

 are still more convex and have a less constricted aperture, while they pre- 

 sent similar differences in the details of the septa. 



Locality and position. — Same as last. 



Scaphites nodosus, var. plcniis. 



Plate 26, figs. l,n, h,c. 



Scaphites nodosus, var. plenus, Meek and Hayden (I860), Proceed. Acad. Nat. Sci. Philad., 420.— Gabb 

 (1861), Synop. Moll. Cret. Form., 33.— Meek (1864), Smithsonian Check-List N. Am. 

 Cret. Fossils, 24. 



This form differs from the. typical Scaphites nodosus, not only in its pro- 

 portionally shorter deflected body-part, but also in its much more gibbous 

 form, and in the smaller size of its inner rows of lateral nodes, which are 

 placed nearer the umbilical side. It also sometimes shows a slight tendency 

 to develop a third intermediate series of very small lateral nodes about mid- 

 way between the other rows, such as I have not seen in any of the other 

 varieties. 



This tendency, however, is only manifested by a scarcely perceptible 

 swelling of the costaa at this point, and consequently, escaped the atten- 

 tion of the artist in drawing the figures ; while even this faint tendency is not 

 constant. 



Compared with the foregoing forms regarded as varieties of S. nodosus, 

 this shell also presents a remarkable contrast, both in form and size. So 

 great indeed is the difference that it seems difficult to believe that it can be 

 properly regarded as even a marked variety of the same species as that 

 represented by our figures 2, a, b, of plate 25 ; and, although I continue here 

 to range it provisionally as a variety of /S. nodosus, I am not altogether free 

 from doubts on this «point. Still, when we come to compare it with Owen's 

 figure of the typical S. nodosus, and with the intermediate forms represented 



